head tail puzzle

For the three coins, there are a total of three heads, and three tails. I think I would agree with you.

I thought it another way though.
Since it already shows a head, it's not possible to be the two-tail coin--it's either the normal coin or the two-head coin. So, for it to show tail on the other side (i.e. to be the normal coin), the possibility is half.

Is this correct?

That sounds like good reasoning, too.

Caveat. I am not a puzzle person.

Umm. On second thought, we have eliminated the coin with two tails. Of the two coins left, you have one tail and three heads. Right? Looks like 3 chances heads, one chance tails, but surely me, you and the book are not all wrong. I like 75% heads.

The answer is 1/3. Since a head was tossed, the coin is either HT or HH. The head that was tossed could be any of three (one on HT, two on HH). Only one of these three heads has a tail on the other side. Therefore, the probability of the other side being tails is 1/3.

Thanks Markr. I think you are right.

The possibility for it to be the HT or the HH coin actually has been changed from 50% given the fact that it already shows heads. In this case, the possibility of being a certain coin is determined by the # of heads that coin has.

Thanks roger for your thoughts too.